Machines for shredding scrap material for disposal are now in extensive use. Such a shredding machine generally comprises a pair of spaced aparts parallel-extending cutter shafts for simultaneous contrarotation in a cutting zone. Each cutter shaft has a plurality of axially spaced apart cutter disks securely mounted thereon. Each of the cutter disks has side surfaces and a peripheral surface which meets the side surfaces defining cutting edges at the intersections thereof. The cutter disks on one of the cutter shafts are interleaved with those on the other of the cutter shafts so that a plurality of the cutter disks on each of the cutter shafts extend into the spacings between the cutter disks on the other of the cutter shafts with a side of each of the cutter disks on one of the cutter shafts overlapping, and being closely adjacent to, a side of one of the cutter disks on the other of the cutter shafts. The machine further includes a feed unit for supplying scrap material such as wastepaper into the cutting zone, and a drive unit for effecting the simultaneous contrarotation of the cutter shafts to "bite" or roll the supplied material therebetween so that respective portions of the material are forced into the spacings between the neighboring cutter disks on the opposite shafts to sever the material into pieces having respective dimensions corresponding to the spacings between the neighboring cutter disks.
In the shredding machine, the peripheral and side surfaces of each of the cutter disks perform important functions. These surfaces serve to "bite in" the material loaded and to be shredded in the machine and thus require considerable friction therewith. It has thus been proposed to form the peripheral surfaces corrugated or toothed to promote the "bite-in" function. The side surfaces to be overlapped when the opposed cutter disks are contrarotated cannot, however, be so formed because they must be closely spaced adjacent to each other while contramoving simultaneously. The peripheral and side surfaces define cutting edges at the intersections therebetween which must thus be sufficiently sharp and maintained so. In the conventional shredding machine, it has been found that these surfaces including regions of their intersections tend to wear so quickly that the machine soon becomes incapable of operating smoothly and even inoperable.